Ashutosh Trivedi

“
My research focuses on applying rigorous
mathematical reasoning techniques to design and analyze safe and secure
cyber-physical systems (CPS) with guaranteed
performance.
I investigate foundational issues (decidability and complexity)
related to modeling and analysis of CPS as well as practically focused
tools that can be used by practitioners to analyze large systems at
scale.
”

Current Research.

Space/Time Analaysis for Cybersecurity.
The goal of this DARPA-sponsored project is to develop new program analysis
techniques to allow analysts to discover Java applications with exploitable
security vulnerabilities such as availability
(denial-of-service) and confidentiality (side-channels) vulnerabilities due to space and time usage
of the programs.
In identifying availability and confidentiality
problems, our focus is to minimize both false positives and false negatives.
In addition, it is often desirable that every identified vulnerability is
presented with sufficient evidence towards an exploit of
the vulnerability. In the case of availability problems, such evidence should
be in the form of an input that triggers excessive resource usage, while for
confidentiality problems, such evidence may a be pair of inputs that result in
differential resource usage.
I am particularly interested in combining static analysis techniques with
run-time analysis to pinpoint program vulnerabilities.
In one of our recent publications [1], we present a new run-time analysis
technique for debugging Java bytecode to uncover potential causes for
side-channels in time.
Related publications: [1],
[2].

Counterexample Sensitivity-analysis for Cyber-Physical Systems. In this
Toyota-sponsored project, I investigate simulation-based approaches to analyze a given set of counterexamples to
correctness properties of CPS towards explaining and widening the
counterexamples to assist the system designer in further debugging.
The resulting approach can be used by engineers to
debug their CPS designs inside practical environments such as Simulink/Stateflow
in MATLAB.
Our approach extends classical sensitivity analysis to generalize neighborhood
of counterexamples by computing a box neighborhood around the original
counterexample so that sampling inputs in our neighborhood is highly likely to
also produce a counterexample. The effectiveness of this approach was
successfully
demonstrated over many CPS models including automotive and closed-loop medical
device control systems.
Related publications : [1].

Theory of Stochastic Hybrid Structures.
The problem of mathematically modeling CPS is fundamental to analyzing their
safety and security properties. However, CPS integrate many different
aspects including time-criticality, nondeterminism,
presence of multiple
rational agents, rich continuous dynamics, stochastic behavior, and
higher-level programming constructs such as heaps and recursion. This poses
a fundamental challenge: a rich combination of these features yields models
that are too complex to reason about. In this project I study several useful
restrictions to these models to characterize the
decidability/undecidability frontier as well as exact computational
complexity of various verification and synthesis related questions.
Parts of this projects were sponsored by a Liverpool-India fellowship,
an IIT Bombay seed-grant, and the Indo-french project AVeRTS.
Related publications : [1],
[2], [3],
[4],
and [5].
Talk (Video) : Multi-Mode
Systems.

Theory of Streaming String Transducers.
The beautiful theory of regular languages is the cornerstone of theoretical
computer science and formal language theory. The perfect harmony among the
languages of finite words definable using
abstract machines (deterministic
finite automata), algebra (regular expressions and finite monoids), and logic (monadic
second-order logic) did set the stage for the generalizations of the
theory to the theory of regular languages of infinite words,
trees, and partial orders.
Alur and Cerny have proposed a model of transducers, called
streaming string transducers, that for regular transformations seems
to be as appealing model as deterministic finite automata for regular languages.
The goal of this project is to study theoretical properties of streaming string
transducers and their applications in verification of CPS.
This project has been supported by the NSF Expeditions in Computing award
1138996 and an IITB seed-grant.
Related publications
: [1],
[2],
[3], and
[4].

Selected Publications.

Discriminating Traces with Time
Saeid Tizpaz-Niari, Pavol Cerny, Bor-Yuh Evan Chang, Sriram
Sankaranarayanan, and Ashutosh Trivedi
In Proc. of International Conference on Tools and Algorithms for the
Construction and Analysis of Systems (TACAS 2017).